This invention relates to a process for the production of dried fruits.
Certain food products of the ready-to-serve type, more particularly intended for breakfast, consist essentially of a mixture of cereals in the form of flakes and dried fruits either whole or in the form of cubes. The cereals used are generally wheat, corn and oats while the dried fruits may be apples, apricots, bananas, figs and grapes, for example.
One of the main characteristics of these food products is the crispy texture of the cereal flakes and the tenderness of the dried fruits. Accordingly, it is important that each of the constituents of the end product retain its own organoleptic qualities in storage up to the moment it is consumed.
Now, the crispiness of the cereal flakes and the tenderness of the dried fruits depend mainly on their water activity value (Aw). Thus, the cereal flakes have a crispy texture when their water activity is of the order of 0.15-0.25. When the water activity exceeds 0.35, the flakes lose their crispiness and become soft. Similarly, the dried fruits have a pleasant tenderness when their water activity is of the order of 0.50 to 0.55. When the water activity falls below 0.40, the dried fruits become hard.
When the end food product is produced and stored by mixing the cereal flakes and the dried fruits, a transfer of moisture can take place so that the dried fruits lose water to the cereal flakes. A balance is generally obtained around a water activity value of the end product of 0.25-0.40, at which the flakes are soft and the dried fruits are hard.
Now, it has already been proposed to treat the fruits with a humectant, such as glycerol, so that they retain a pleasant and tender texture for a water activity value below 0.50. To obtain good absorption of the humectant in the fruits, it is preferable to increase the permeability of their skin by pretreatment before they are steeped in the humectant.
Thus, it is known, for example from Canadian Patent No. 981,523, that the fruits can be subjected to a hot pretreatment with a weak acid and then to treatment with a humectant, such as a solution of sorbitol or glycerol, for about 15-24 hours so that the fruits absorb at least 3% humectant. The fruits thus treated are then dried to a dry matter content of 80to 88%.